Paul Gerhard Natorp was one of the most prominent philosophers inGermany at the turn of the last century. Born in Düsseldorf onJanuary 24, 1854, he began his university education at Bonn inclassical philology under Hermann Usener, and continued at theUniversity of Strassburg, but as he neared completion of his studies,he found himself unsatisfied with his work, and vexed by “asecret philosophical urge” (Natorp 1921f: 152–153; alltranslations by the author). It found its outlet when a friendstudying at Marburg wrote to him of Hermann Cohen and F.A. Lange, andof their interpretation of Kant; thenceforth Natorp “placed hiswhole thinking and his entire, powerful capacity for work in theservice of thissingle task:” the development of“philosophy as science” (Cassirer 1925: 276). His firstphilosophy teacher was Ernst Laas, whose anti-Kantian andanti-Platonic positivism incited Natorp to deeper engagement with thephilosophy of critique (Natorp 1921f: 153). In this way, his earlyphilosophical studies converged with his original love of philology ashe pursued the “prehistory” of Kantian critique inDescartes, Galileo, and Copernicus, back to Plato (Natorp 1921f: 154).Natorp completed hisHabilitation under Cohen at Marburg in1881, and taught there until his death on August 17, 1924.

During his long and prolific tenure at Marburg, Natorp came intocontact with a number of illustrious scholars and writers. BorisPasternak, Karl Barth, and Ernst Cassirer were among his students;Rabindranath Tagore was his friend. In the fateful summer of 1914 theyoung T.S. Eliot caricatured Natorp, the director of the summerprogram in which he was enrolled [image available online]. In addition to Cohen, academic colleagues included the philosopherNicolai Hartmann, the theologians Rudolf Bultmann and Rudolf Otto, andthe literary scholar Ernst Robert Curtius. Late in life, Natorpdirected Hans-Georg Gadamer’s doctoral dissertation (Gadamer1922), and, together with his long-time philosophical interlocutor,Edmund Husserl of Freiburg, engineered Martin Heidegger’sappointment as anExtraordinarius at Marburg in 1923. UponNatorp’s death the following summer (see Heidegger 1992),Heidegger assumed his chair, thus bringing the department’sKantian orientation to a decisive close.

Like his younger contemporary, Ernst Cassirer, Natorp initiallyfocused on the explication, defense, and elaboration of Cohen’sdifficult and often impenetrable work on Kant-interpretation, thetheory of science, and the history of philosophy.^[1] While Natorp published important works of contemporary systematicphilosophy (1887, 1888h), he devoted much of his attention in the lastdecades of the nineteenth century to filling out historical elementsin Cohen’s larger framework. He especially employed hisexpertise in Greek thought to work out ancient anticipations of“critical” scientific philosophy, and analyze its naturaldevelopment. Later, in the chaotic social, political, and culturallandscape of pre- and interwar Germany, and especially in the wake ofCohen’s death in 1918, Natorp departed from the classic Marburgconcentration on the logic of the exact sciences. This departure wasless a shift in his basic philosophical outlook than the sounding ofnew themes, some native to the Marburg School, others arising out ofdialogue with other philosophers. Motivated by the liberal-socialist ideals^[2] integral to the global theory of culture that was theMarburgers’ ultimate aim,^[3] Natorp wrote widely on ethics, politics, andSozialpädagogik.^[4] On the other hand, one must also interpret Natorp’s laterthought (esp. his “ontological turn”; von Wolzogen, 1988; Brach 1996) in light of hisdialogue with other philosophies challenging neo-Kantianism’sdominance in the German academy, notably the so-calledLebensphilosophie, and the phenomenologies of Husserl and Heidegger.^[5]

• 1. Natorp and Marburg neo-Kantianism
• 2. Transcendental method in the philosophy of science
• 3. Method and hypothesis
• 4. Thinking
• 5. ‘Critical’ Psychology
• 6. History of Philosophy
• Bibliography
  • Works by Natorp
  • Secondary Sources
  • Related Works
• Academic Tools
• Other Internet Resources
• Related Entries

1. Natorp and Marburg neo-Kantianism

Neo-Kantianism, it is often said, was the dominant current of latenineteenth-century German academic philosophy. While true, thisstatement is uninformative, since the label conveys no clear doctrinalcontent. Given the widespread perception that philosophy had becomediscredited by the untenable claims of the German Idealists, thevarious neo-Kantian schools shared a conviction that Kant—onsome interpretation of his sobriety—could give philosophy arespectable and genuine task again, now that it had awakened from itslong post-Hegelian hangover (cf. Natorp 1918a: 4–6; Dussort1963; Schnädelbach 1983a, 1983b; Köhnke 1986; Philonenko 1989; Sluga 1976: 28). Thelabel therefore does not necessarily signify a revival of Kant’sdoctrines (much less of Kant-scholarship for its own sake^[6] ), but rather, as Natorp himself puts it, philosophizing in thespirit of Kant (Natorp 1918a: 7). But what does that mean? For theMarburg School, Kant’s great idea, “the central notionwith respect to which one must relate, understand, and evaluateeverything else in Kant” is thetranscendental method(Natorp 1912c: 194; cf. Cassirer 1925: 288). This method constitutes“the unshakeable guideline of our whole philosophizing”(Natorp 1912c: 196). Why? Because the transcendental method anchorsphilosophy in facts (eminently the fact of mathematical physics),of which philosophy is to establish the conditions ofpossibility or justification (Rechtsgrund) (Natorp 1912c:197; 196). By limiting itself to this task of justification,philosophical reason keeps itself from ascending into the aether ofspeculation. At the same time, by discovering the source of scientificobjectivity (and thus of rational objectivity generally), i.e., by“clearly exhibiting the law [of objectivity] in itspurity”, philosophy “secures science [and rationalactivity generally] in its autonomy and preserves it from aliendistraction” (Natorp 1912c: 197–198). Transcendentalphilosophy in the Kantian spirit, then, is doubly“critical”, checking itself against metaphysical excesses,on the one hand, but also rigorously formulating the ideal grounds ofthe sciences, on the other (Natorp 1912c: 198; cf. Poma 1997, ch. 3,4). At the same time, the Marburg School finds in the criticalphilosophy an idealistic bulwark against the empiricism epitomized byMill.

Moreover, the Marburgers endorsed Kant’s view that philosophyshould adopt an approach to the other domains of humanculture—morality, art, and religion—that was“critical” in just the transcendental sense describedabove. This approach, then, takes the critique of science as theparadigm of philosophy’s relation to culture in general. Just asthe critical theory of science begins from the concrete theoriesdeveloped by the special sciences, so philosophy in general shouldbegin from the achievements of culture (e.g., works of art, moralaction or institutions), and investigate the basis of their claims.This is one reason Cohen and Natorp call their critical philosophy“idealism”, because its task vis-à-vis culture isto lay out the system of rational principles that make possible the“facts” of science, morality, and art. At the same time,their idealism aims at making explicit the “ideas” thatguide, or ought to guide, the continuous development of culture.Finally, the Marburgers’ very theory of transcendentalprinciples is itself “idealistic” in the radical sensethat all objects of experience are held to be the products solely ofthe activity of thinking. Nevertheless, Marburg theory deniesphilosophy any “speculative” task of seeing or knowingthings that are beyond experience, of constructing systems of ideasthat are not immanent in the facts of human knowledge, action, orproduction. Like Cassirer, Natorp makes this view of philosophy in theKantian spirit the basis of his own philosophy of science and of hishistorical interpretations.

One main reason why neo-Kantians of all stripes see the essence ofphilosophy in critique is that it guarantees philosophy’sautonomy (cf. Natorp 1887: 266–269, 285,et passim). Ofall rational activities, philosophy alone has the task of discoveringthe conditions and regulative ideals that make such activities at allpossible. While the problem of philosophy’s identity as adiscipline of course goes back to Plato, we are faced, in thenineteenth-century German context, with the particular problem ofphilosophy’s relation to the positive sciences, which hadcompletely repudiated and replaced the knowledge-claims of thespeculative systems of German Idealism. For the Marburgers, the issueof philosophy’s disciplinary integrity becomes intertwined withthe question of the autonomy of reason itself. Cohen and Natorp faceda difficult task. Having turned their backs on speculative philosophy,they could not define reason’s autonomy by falling back upon thediscreditedGeist of German Idealism.^[7] But they also could not let reason (or as they prefer to call it,“thinking”) be conceived as a set of psychologicaloperations, since that would subject reason’s laws (logic) tomore basic psychological or psychophysical laws. Already in his(1887), Natorp objects to such psychologism (though he does not usethe term) on the grounds that science and knowledge, and the verynotion of objective truth these presuppose, would be renderedsenseless if grounded in thesubjective experience of thethinking or knowing psyche (see esp.Section 4). The chief task for any account of Natorp’s philosophy, then, isto make sense of his notion of rational autonomy.

Beyond the issue of reason’s autonomy or priority, anothercentral issue for Natorp is reason’s history; again, this is aconcern typical of the Marburg School generally; one of itspeculiarities is the quasi-Hegelian insistence upon the integration ofthe systematic and historical moments of philosophy. Cohen wrote majoressays on Plato (Cohen 1866, 1878), and Natorp’s early workconcentrated on what the Marburgers considered ancient and earlymodern anticipations of the critical philosophy. Then there isNatorp’smagnum opus,Platos Ideenlehre of1903, in which he simultaneously develops a “critical”interpretation of the theory of forms and an argument for the order ofthe dialogues, all conceived as an “Introduction toIdealism” (cf. Laks 1994, 2003).

During his life, Paul Natorp was overshadowed by his mentor, Cohen,and after his death, by the more glamorous Cassirer. For decades, ifhe was mentioned at all, one remembered his controversial Plato book,or, perhaps, his other contributions to the study of Greek thought(cf., e.g., Stewart 1909; Owens 1978; Gaiser 1969). But Natorp hasbeen further obscured by the general eclipse of neo-Kantianism formost of the twentieth century.^[8] It has only been since the late 1970’s, with the revival ofEuropean interest in the Marburg School, and especially through thework of Helmut Holzhey since the 1980’s,^[9] that Natorp has reappeared on the philosophical scene and the uniquefeatures of his thought have become more plainly distinguished from Cohen’s.^[10] Holzhey’s unearthing of several heterodox, critical texts(Holzhey 1986: vol. 2) from theNachlass suggests that Natorphimself had suppressed them, either “for the sake of maintainingthe unity of the ‘Marburg School,’” or because hedid not always think himself able to provide an alternative to aparticular Cohenian thesis.^[11] Yet, despite the Marburgers’ loud assertion of the centralityto their philosophy of science and its history, most recent interestin Cohen has focused on his late works in the philosophy of religion;and despite Natorp’s allegiance to Cohen’s generallyscientistic program, much ado is made of his purported“ontological turn” (cf., e.g., Brach 1996: 190, ff.;Stolzenberg 1995, ch. 5) away from epistemology. By contrast, thisarticle focuses on Natorp’s thought in the areas to which heafter all devoted most of his career as a member of the MarburgSchool: philosophy of science, history of philosophy, andphilosophical psychology; it does not deal with his politics orpedagogical theories (see esp. Willey 1978; Jegelka 1992; Natorp1905), philosophically informed though they are (Cohen 1914: 470).

2. Transcendental method in the philosophy of science

It is a commonplace of nineteenth-century German intellectual historythat with the collapse of post-Kantian Idealism, philosophy ceded itsclaim of scientificity to the positive sciences.^[12] The special sciences made rapid and startling progress, continuallyadding to the store of human knowledge. Philosophy, meanwhile, seemedto have lost its way, and many thinkers pinned their hopes for arehabilitation of philosophy on a return to Kant. The Marburg Schoolin particular interpreted this to mean that philosophy should orientitself with respect to the sciences, rather than strive—asGerman Idealism had—to forge a scientific system of its own,independent from the results of the positive sciences: only in thisattenuated sense would philosophy be “scientific”. For allthat, Natorp by no means conceived philosophy as a humble handmaiden.On the contrary, its task is to discover and establish the highestprinciple(s) of rational understanding, and thereby the principles notonly of the sciences, but also of ethics and aesthetics, in short, ofall the domains of human culture (cf. Cohen 1902: 443). It musthowever take science as its primary object of inquiry because sciencerepresents the paradigm of knowing (Erkenntnis). Only acritique of science can therefore elucidate rationality or, as theMarburgers call it, the “logic” of thinking, for it isonly in science that we can most reliably witness thinking at work,successfully achieving knowledge. Thus the question of the“concept of science” becomes “the chief question oflogic and the foundational question of philosophy” (Cohen 1902:445). The Marburgers identify the unifying principle of science andethics in particular^[13] as the concept of law (Gesetz), and, as Cohen puts it,“it is the business of logic to determine the meaning of law, orrather, the meanings of law” (Cohen 1902: 445).

Natorp and Cohen find general affirmation of this train of thought inKant’s project of seeking the conditions of possibility of the“fact” of mathematical natural science (cf. KantProlegomena). However, the similarities end there, for byrejecting or modifying several basic aspects of Kant’sphilosophy, they also end up with a radically transformed conceptionof the nature of scientific experience and the meaning of knowledge.The first of their modifications stems from an anti-psychologisticcritique of Kant himself, namely of what they see as a confusion inthe firstCritique between the task of a transcendentalgrounding of the sciences and that of a transcendental logic of humancognition (Stolzenberg 1995: 25. But compare Holzhey 1984: 137). Theformer is in their view the genuine critical enterprise, for itpromises to reveal the autonomous sources of objective knowledge,whereas the latter threatens to trace science back to psychological,and therefore contingent, subjective (albeita priori) wellsprings.^[14] Second, they deny any scientific role to intuition as conceived byKant, either pure or empirical. Partly this is a result of theiranti-psychologism, which forbids them from grounding the objectivityof science in the subjective faculties of cognition; but it is alsobecause they see, with Kant, the essence of thinking in its activityand spontaneity, whereas intuition (at least as defined by Kant) ispassive and receptive (cf., e.g., Kant,Kritik der reinenVernunft (KrV), A68/B93). Hence, intuition thusconceived threatens to introduce a heteronomous, and thereforerationally unacceptable, factor into science. Finally, the Marburgersfollow their German Idealist predecessors in dismissing all talk ofthings in themselves, conceived as things existing independently ofknowledge. We can see how these three important modifications ofKant’s philosophy stem from the same basic concern with rationalautonomy. For reason to be autonomous, its activity must bespontaneous; but this spontaneity cannot be conceived ofpsychologically, because human cognition as a matter of fact has apassive, and therefore heteronomous, intuitive element, namelysensibility. Furthermore, things in themselves can play no explanatoryrole here because they areex hypothesi alien to reason.

These modifications have two radical consequences for Kantiandoctrine, consequences that characterize the Marburgers’ owntheory of science and cognition. The first is a new conception ofscience; the second is a new conception of the categories (seeSection 4). It might seem that science, as the achievement of an autonomousrationality, must fail to be objectively true of the world, ifreason’s autonomy implies that it can have no intuitive,receptive link to the world via sensibility. How in general could therationally constructed system be related to experience or constrainedby it? How in particular could physics, the science of motion in spaceand time, be possible if the pure forms of intuition, space and time,were banished from science (cf. Friedman 2000: 26, ff.)?

If Natorp often seems to embrace the troubling thesis that science isnot of the phenomenal world, this is because he holds, first, that themeaning of “phenomenon” is problematic; and second, thatthe aspect of sciencerelevant to philosophy has nothing todo with its relation to a phenomenal realm. In this he followsCohen’s dictum:

Not the stars in the heavens are the objects which [thetranscendental] method teaches us to contemplate in order to knowthem; rather, it is the astronomical calculations, those facts ofscientific reality which are the “actuality” that needs tobe explained…. What is the foundation of the reality which isgiven in such facts? What are the conditions of that certainty fromwhich visible actuality takes its reality? The laws are the facts, and[hence] the objects [of our investigation]; not the star-things.(Cohen 1877: 27, f.)^[15]

The point is that the scientific or epistemic value of, say,astronomy, is not to be found in what is given and observable by thesenses, but rather in the mathematical exactness of its equations.These alone constitute and underwrite the truth-value ofastronomy’s propositions, and they are solely the achievementsof reason’s activity. As noted above, the essentialcharacteristic of science lies in its objectivity, and thatobjectivity is rooted in its lawfulness. It is this formal feature ofobjectivity that constitutes the philosophical interest in science,not the material content of a particular science’s theorems; inother words, the philosophical question is: “How is thislawfulness possible?” This question is distinct from thepsychological question, “What are the psychological laws thatmake it possible for me (as a psychophysical being) to observe astar?” or the astronomical question, “What are the lawsgoverning the ’being’ of this star in its states andproperties?”

Hence, it is not so much the case that science on theMarburgers’ conception loses all traction on the phenomenal or“actual” world, as that they are asking an entirelydifferent question. While for Kant himself such traction is the onlywarrant that we are cognizing a genuine object, for Natorp the nexusof science and apparent reality is irrelevant to the spontaneous,legislating factor of science that is the activity of reason alone andtherefore of paramount interest to philosophy. How such essentiallysubjective application of categories to sensible phenomena in facthappens is a problem of psychology, not philosophy, to investigate.Thus we must be very careful in interpreting the Marburg talk of“scientific experience”: it is not experience in generalor psychological (subjective) experience (Erlebnis), butscientific (objective) experience (Erfahrung) which is the“fact” whose transcendental sources philosophy is to seek(cf. Natorp 1910c: 13). Yet we mustnot in turn take thisscientific “experience” to mean “experience cleansedby experiment” (to paraphrase Helmholtz^[16] ): experiment by definition obviously remains empirical. Rather, by“scientific experience” Natorp just means the“legislative” act of categorial “Grundlegung”,of “hypothesis”.^[17]

By the end of the nineteenth century, it was obvious to any informedobserver of science that its categorial structures were in facthypothetical and dynamic: the fact of scientific experience could nolonger be taken as the essentially complete edifice of Newtonianphysics, as Kant had done. In Natorp’s rewording of Kant,science is not afactum at all, but afieri, i.e.,not an accomplished deed, but an ongoing doing (cf. Natorp 1910c: 14).Hence, what makes science scientific—i.e., productive of genuineknowledge—cannot possibly be founded on a set of fixed(physical) principles, analogous to mathematical axioms, the certaintyof which permanently grounds its theorems. Instead, the Marburgersargue, the essence of science can only reside in itsmethod,i.e., in the regular and regulated manner of its progress. And sincethis scientificity is equivalent to objectivity or lawfulness,transcendental critique must determine the relation of lawfulness tomethod.

3. Method and hypothesis

In his memoirs, Hans-Georg Gadamer calls Natorp, his doctoralsupervisor, a “Methodenfanatiker” (Gadamer 1977:62). By this Gadamer means that Natorp, for most of his career,focused on the methodical aspect of thinking to the point of reducingthinking to method. To understand this riddling statement, one musttake into account Natorp’s interpretation of the word,“method”. He writes:

The word “method”,metienai, implies not a mere“going” or movement in general; nor, as Hegel believes, amere accompanying [going-with]; rather, method means a going towards agoal, or at any rate in a secured direction: it means“going-after” [pursuit].^[18] (Natorp 1912c: 199–200)

The directedness towards a goal which Natorp claims is implied by“method” illuminates one of two senses^[19] in which his philosophy is idealistic, namely that science (and theother activities of culture) are guided by regulative ideas orlimit-concepts (Grenzbegriffe). Ideas, as Kant argues in theTranscendental Dialectic, area priori concepts whose sourcelies in pure reason alone. Their only legitimate—thoughindispensable—theoretical use is to regulate theunderstanding’s cognition of objects: reason sets down theconditions under which the understanding’s activity will haveachieved its ideal completion in the systematic interconnection of itscognitions, i.e., in an ultimate science. Reason thereby offers theunderstanding a rule—viz. maximal scope and maximal internalsystematicity—against which any actually achieved system ofscience must be measured; and because human finitude makes itimpossible in principle for any actual system to attain the idealmaximum, reason also spurs the understanding on towards ever newdiscoveries and reorganizations.^[20]

While Natorp often seems to blur the distinction between Kantiancategories and ideas, collapsing them both into“hypotheses” (see below), there is one notion that doesfunction as an ideal: theDing an sich. According to Natorp,the thing in itself, properly conceived, is a “purelimit-concept [Grenzbegriff], which merely delimits[begrenzt] experience in its own creative legislation”(Natorp 1912c: 199); more precisely, the thing in itself is not somemind-independentX, but rather anX necessarilyimplied by the fact of scientific progress, namely the“comprehensive sum total [Inbegriff] of scientificknowledge” (Natorp 1918a: 19). Because science is an activity ofreason alone, and the thing in itself is a rational posit necessaryfor that activity, it is no longer in conflict with the postulate ofreason’s autonomy. Given an object of scientific cognition, thecognition is conceived as a process never “definitivelyconcluded”, as Cohen says; rather, “every true concept isa new question; none is a final answer” (Cohen 1885, cited atNatorp 1918a: 19). Natorp comments: “Just this is the meaning ofthe thing in itself asX: the infinite task” (Natorp1918a: 19). In other words, the thing in itself is the ideal of anobject exhaustively determined by concepts, that is, completely known.As with Kant, however, our cognitive finitude means that the processof conceptual determination can only approach this ideal asymptotically.^[21] This pursuit of total determination is what Natorp calls“method”, the pursuit of science.

This brings us to the key notion of “hypothesis”. Thepursuit of science—its “method” in Natorp’sspecial sense—proceeds by hypothesis. Sometimes he puts it morepointedly: hypothesisis method. Since method is for him a“going-after” or pursuit of the “perpetually distantgoal” (Natorp 1910c: 97) orfocus imaginarius ofcomplete objective determination, Natorp interprets“hypothesis” in a correspondingly active sense. He takesthe term “hypo-thesis” quite literally as a“setting-down” or “laying-under”, or as heputs it, a “Ge-setz” or“Grund-legung” (cf. Cohen 1902: 449; 1916: 308,ff.). These glosses all emphasize the activity of hypothesis: it isless a posit than a positing, an act by which thinking proceeds andbecomes experience. Natorp writes:

The risk [Wagnis] [of hypothesizing] is inevitable if theprocess of experience should begin and continue moving: just as myfoot must take a stand if it is to be able to walk. This taking astand is necessary, but the stand must in turn always be left behind.(Natorp 1912c: 203)

The act of hypothesis has two aspects.^[22] First, hypothesis as law (Gesetz) or groundwork(Grundlegung) is the transcendental foundation for scientificexperience, i.e., for the activity of legislating and thus rationallyunderstanding the phenomena. The “phenomena” in questionare not however the sensible phenomena of subjective, psychicexperience (Erlebnis), but are instead themselves alreadyconstructions or interpretations. These constructions in turn arefounded on hypotheses of a lower order, viz. on specific conceptsformulated to transmute particular subjective experiences intoobjective knowledge. To take up our earlier example, when theastronomer speaks of planets and their laws of motion, he is speakingobjectively ofscientific phenomena, as opposed tothesubjective appearance ofsensible phenomena toyou or me. Therefore, on Natorp’s view, strange as it may sound,the phenomenon “Mars” is an hypothesis, an objectcertainly, but for all that an ideal and never fully determinedthought-object; moreover, the motion of this object, too, isideal: it can be calculated with the utmost exactitude. It is thesetwo hypotheses—the concept, “Mars”, and the lawsgoverning its motion—that alone are objective, and susceptibleto knowledge; the reddish speck in the sky is merely a subjectiveappearance, of which there can be no genuine (astronomical)science.

To pull our strands together, thinking in the strict sense isscientific thinking, for it alone is generative of knowledge, i.e.,objective truth. Science (and therefore knowledge) as a matter of factevolves through time: science is afieri. However, thisevolution orfieri is not unregulated, but moves in acontinuous pursuit of ever more precise determinations of experience:this pursuit is literally called “method”. Thesedeterminations of experience just are the objects of science. Thephilosophical task therefore is to analyze the condition ofpossibility of theregularity of this methodicaldetermination of experience. Natorp (like Cohen; 1902: 449) identifiesthis condition as hypothesis, interpreted as law (Ge-setz,posit); experience in the strict sense is only possible given a law(Gesetz) that functions as its interpretational groundwork orfoundation (Grundlegung). The first hypothesis or primalposit then must be the law of lawfulness, viz., the rational postulatethat experience, in order to beErfahrung, and not mereErlebnis, must accord with law, i.e., be grounded on arational foundation (cf. Natorp 1887: 285; 1911e; 1917: 246). Thiscategorical imperative, that all its experience fall under law, is theoriginary act of reason wherein lies its ultimate autonomy; it is theregulative principle of the continuous, orderly flow of experience.^[23] As a general, purely formal law it regulates the particularhypotheses, which in turn generate or ground particular objects ofErfahrung (such as “Mars”,“electricity”, “atom”, or“gravity”) in the regulated process of their ever widerand ever more rigorous determination.How it does this is aseparate problem, one that Natorp attempts to solve through his systemof categories, treated in the next section.

4. Thinking

Just as “experience” for the neo-Kantians is restricted to“scientific experience”, so too is “thinking”restricted to “scientific thinking;” in fact, Natorpvirtually conflates experience and thinking. His view of science asthe progress (Gang) of method via hypotheses regulated by anideal of complete objective determination leaves the problem of whatexactly these hypotheses do and how they do it: the problem of Marburg“logic”. As Cassirer points out, Natorp’s conceptionof logic presses the traditional “analytic” doctrines ofconcept, judgement, and syllogistic into the background in favor ofthe “synthetic” logic of the genesis of mathematical andphysical objectivity.^[24] Natorp’s logic is therefore called “genetic;” ittells how thinking lawfully generates or synthesizes the unities thatare its objects of knowledge. As such however it amounts to ananalytic reconstruction of thinking’s synthetic construction ofits objects (Natorp 1887: 283). He writes:

It is true that thinking operates [schafft] (in the sciences)in accord with secure laws of synthesis, although to a large extent itis at the same time unconscious of these laws. [As science] itsinterest is not primarily these laws, but rather the scientificcontent which is generated in virtue of them. Thinking is in each casefocused upon its particular object. An entirely new level ofreflection is required to investigate, not the particular object, butthe laws in accordance with which this and any scientific object ingeneral first constitutes itself as an object. This new kind ofreflection we call “logic”. (Natorp 1910c: 10–11)

In other words, the scientific hypotheses or laws (Ge-setze)by which science methodically, synthetically progresses are nottransparent to rationalityqua scientific; instead, they mustbe analogically retraced by a critical “logic”.

For Natorp, as for Kant, thinking is activity, doing: the technicalterm is “function”. This word, however, is as ambiguous asit is central to the Marburg account of thinking.^[25] Occasionally, “function” seems to mean something likesubjective, psychic act, and as such is excluded from epistemologicalconsideration (Natorp 1887: 266); usually, however, it signifies thespontaneity of thinking, not in psychological terms, but as therational act of hypothetical legislation discussed earlier. In thissecond signification it is sometimes connected with“function” in the mathematical sense, or else mathematicalfunctions are adduced as paradigmatic of the functional conception of thinking.^[26] The standard sense of “function” for Natorp, then, isthat of an act or “operation” of thinking, where thismeans laying down a hypothesis. Since the hypothesis is always aconcept, a generality that imposes a unity upon a phenomenal manifold,we can understand “function” more precisely as the act ofunification or synthesis.

For Kant, too, the term, “function”, is always connectedto the categories’ spontaneity and their synthetic activity;further, he holds that truecognition (Erkenntnis)can only occur if the synthesis in question “schematizes”representations given in intuition (cf. Young 1992; Friedman 1992,2000). By contrast, Natorp understandsall concepts asfunctional, i.e., as categorial, since all of them, including theconcepts of space and time, are thought-operations serving to unify a manifold.^[27] As we saw above, Natorp rejects any notion of intuition as a passivefaculty receptive of a given sensible manifold (cf. Natorp 1912c:201). Instead, he interprets intuition as itself an act of synthesis,i.e., as a generation of unity. He argues that a critical account ofknowledge is not justified in presupposing some object conceived asexisting radically independent of mind, and which then somehow affectsit via intuition: to do so would be tantamount to an intolerable“metaphysicism” (Natorp 1912c: 202). Rather, Natorp claimsto find in the firstCritique itself the basis for his viewthat intuition is not a factor “alien to thought[denkfremd]”, but that it merely signifies a differentaspect of thinking, viz. that aspect in which a fullyspatio-temporally determined object, rather than merely a law, isthought (Natorp 1912c: 204; Natorp 1910c: 2–3). This“fulfillment [Vollzug]” of objective thought

in each of its stages requires rigorously unambiguous determination,but determination always with respect to the lawful functions ofthinking itself: determination of the particular, of quantity, ofquality, in accord with the relation of causality and its laws.(Natorp 1912c: 204; Natorp 1887: 280)

On this view, far from being separate from and opposed to thinking asthey seem to be in the firstCritique, space and time, as theforms of intuition, are originary thought-acts that make possible thedetermination of any object whatsoever. They are hypothesized,synthetic manifolds, or—more precisely—unified, orderedmanifolds of points or “positions” (Stellen) intowhich any object must first be integrated if it is to undergo anyfurther determination as to quantity, quality, etc. (Natorp 1912c:203; 1887: 280. Cf. esp. 1911e: 76–77;PI, 159, ff;366, ff.). Thus, only in virtue of these various synthetic proceduresof progressive determination, which Natorp calls“objectivation” (i.e., object-formation), can a phenomenoneven appear. But how does it appear? Since intuition and thinking arebeing analyzed here entirely at the “functional” level,the phenomenon evidently doesnot appear as a sensibleobject, i.e., one that may be assigned a unique set of spatio-temporalloci, and that then may serve as a carrier (Träger) ofall further determinations of quality, quantity, or relation.

This then raises the following pressing question: if, as he argues,intuition is itself a synthetic activity, what “matter”does it synthesize, if not the sensible manifold? Natorp isdistressingly elusive on this point, even in his explicit discussionsof the status of time and space in science (cf. Natorp 1910c: Chapter7). The following is clear, however. Like Kant, Natorp understandsthinking always to be thinking an object. For Natorp, however, thismeans “constituting”, “constructing”, or“objectivating” the object. But since he (re)interpretsthese objects as non-sensible phenomena, he also interprets space andtime non-psychologically, i.e., as non-sensible. They are not theforms of sensible intuition, but the ideal system of dimensions (threespatial dimensions plus time (cf. Natorp 1910c: 303, ff.;397–398), conceived as

structures of a purely mathematical kind, which nonetheless go beyondmere number, in virtue of the general relation to existence [that is]contained in their very concepts. (Natorp 1910c: 341)^[28]

Thus a very crucial distinction must be made between two levels ofphenomenality and of objectivity, which for the purposes of thisarticle shall be called “first-order” and“second-order” (cf. Stolzenberg 1995: 25). A first-orderphenomenon is the psychic,subjective appearance that Natorptacitly acknowledge has a basis in sensibility, and which he calls the“Phänomen letzter Instanz” or the“phenomenon of final authority” (Natorp 1887: 273, 274;1913b: 192);^[29] this first-order phenomenon is a “Vorstellung”,or “representation”, i.e., a doxic phenomenon (Natorp1887: 266, 267; esp. 273). Hence it cannot be the referent ofknowledge or science, since science does not concern itself with doxicappearancesas such, but theobjects (orobjectivities) which appear in or through the appearances (Natorp1913b: 193).

But how are we to understand this “appearing” of an object“through” the doxic appearances? What, precisely, is therelation between the first-order and second-order“phenomena”? In the places where he explicitly mentionssensibility in the concrete, psychological sense (Natorp 1913b: 193),Natorp conceives it as never conveying or “giving” themind an object, ready-made. Rather, “what” sensibilitygives is so entirely indeterminate and uncoordinated that it cannoteven be called a manifold; whatever the chaos of sensibility may be,Natorp conceives it as nothing more than atask(Aufgabe),problem, ordemand(Forderung) for objectivity, that is, objectivation.^[30] Since no thing (no object) is ever given in sensibility, any objectis only ever constructed, and can only be knownquaconstruction, viz. as an instance of its constituting law.

Natorp likens this problematic relation of first-order phenomenalityand second-order objectivity to solving forX in an equation(Natorp 1887: 258, 262). If the solution(-set) ofX is theobject for which thinking is to solve, then the sensible appearance isanalogous to the notational cipher, “X”, itself,since what-has-not-yet-been-experienced is simplywhat-has-not-yet-been-constructed. Moreover, just as in solving anequation one can only determine theX in light of other knownquantities assumed in the equation, one must in the same way establishthe determinations of the problematic object in light of otherobjectivities (laws) that are assumed (ge-setzt). No suchobjectivities are ever granted absolutely, of course, but onlyrelatively, namely with respect to the particular problem. They, too,are always susceptible to becoming problems in their turn. Thereforeno complete solution—no total determination of theobject—can be achieved for anyX, exceptasymptotically. While the fully determinate object itself thus remainsa forever unreachablefocus imaginarius (seeSection 3), it is, by the same token, always at least partially determined. Andit is thispartially determined objectivity as itself a(non-sensible) object of thinking that Natorp considers thesecond-order phenomenon, even though he will usually just call it a“phenomenon”,simpliciter. Thisscientific phenomenon, as an objectivity that isprogressively constituted by a dialectic between hypothesis andcalculation, entirely loses any sense of “appearance”.This reconception of the phenomenon of mathematical physics finds ananalogue in geometry’s replacement of constructions “inintuition” by purely logical deductions fromGrundlagen(or “functions” in the sense of “hypotheticalact”) as epitomized by Hilbert’sGrundlagen derGeometrie (cf. Friedman 1992, Chapter 1; Hilbert 1999), a bookcited with approval by Natorp (1910c: 4) and Cassirer (2000: 99, f.).

The question now is: what makes the second-order phenomenon a bonafide objectivity, in contrast to the first-order phenomenon? Whereasthe first-order phenomena constitute private, lived subjectivity, notopen to prediction or even adequate description, Natorp’s answeris that the second-order object is constructed in accordance with lawsof thinking, which as laws are in their very nature objective, i.e.,universally valid for any thinker. Therefore objects(Gegenstände) lawfully determined will in principle berationally transparent to any other thinker, i.e.,“objective” (objektiv,gegenständlich). Any such lawful objectivation orobject-formation just is knowledge or science, in the sense of beingobjectively thinkable. These laws of constitution are in turnhierarchically arranged: the highest, most general laws are thosegoverning all possible thinking, and thus the generation of allexperience. These are followed by mathematics, and by all themathematically “exact” sciences. As was shown inSection 3, Natorp conceives these laws (Ge-setze) asessentially “hypothetical”, that is, ascategorial posits. With the apparent exception of the basic logicallaws (e.g., the indispensable “law of laws”),allsuch laws are in principle revisable (which is chiefly why thedetermination of objectivities must be conceived as asymptotic)(Natorp 1887: 274; 276–277).

Hence, philosophy, as transcendental critique (seeSection 1), is “sharply distinguished from any kind of‘psychologism’” and “maintains its rigorouslyobjective character” (Natorp 1912c: 198).^[31] Why? Because its point of departure is theobjective“formations” [Gestaltungen] of human culture,as objectivities, not as products of subjective psychologicaloperations (Natorp 1912c: 198). In other words, philosophy alwaysbegins from the second-order phenomena.

5. ‘Critical’ Psychology

Although on Natorp’s view, the first-order phenomena ofsubjective psychological experience (Erlebnis) eludescientific understanding altogether, he wrote two significant works onwhat he calls “critical” psychology. Pure,unconceptualized subjectivity is the immediate condition of thepsyche; but the “logos” of science just means“objectivity”. Hence, Natorp argues, there can be no“psycho-logy” in the strict sense of the term, for itwould amount to the objectivation of subjectivity, and hence to theannihilation of the very thing a psychology would want to study: thepsyche in its “natural” state (cf. Natorp, 1887: 283).Although there is no

immediate access to the immediacy of psychic experience, [yet] it can… be approached by a [methodical] regression from itsobjectivations, which must therefore [first] be secured in their ownpurely objective justification. (Natorp 1912c: 198)

This is “critical” psychology in a nutshell. What Natorpmeans is this: there can be noobjective “access”to immediate psychic experience, which is absolute subjectivity.Nonetheless, we can gain access to amediated subjectivity,namely through the objects that have already been objectivated in(scientific) thinking.

Thinking, as we saw inSection 4, moves forward in a “synthetic” fashion from the less tothe more determinate. That is, in taking up a second-order phenomenon,thinking works on an object that retains,qua appearance(phenomenon), an as yet undetermined subjective, doxastic residue. Itbrings (some of) this residue under laws, thus determining the objectfurther: it is now better known and scientifically understood. Now,instead of seeking the constitutive legislative framework thattranscendentally “grounded” that determination (the taskof critical philosophy), criticalpsychology performs a“methodical regression”, viz., by undoing theobject’s most recent determinations, thus revealing its prior,relatively more “subjective” phase.

In this way, Natorp thinks, antecedent stages of our latter-dayscience can be reconstructed and temporarily resuscitated. Thisproject complements critical philosophy’s logical project, byallowing reconstruction of successive phases of objectivity, thusmaking our current knowledge more transparent toreflective reason.^[32]

6. History of Philosophy

We finally turn to the Marburg thesis that philosophy, as philosophyof science, must also be the philosophical history of science. Forscience, as afieri (a doing) evolves over time;hence the activity of its basic functions and the regulated mutationof its laws can only be observed through time. Yet this historicaltracing of the progress of science must be philosophically informed,that is, grounded in the transcendentally isolated system of basicfunctions. As mentioned above, Natorp holds that the entire value ofthe transcendental method is normative: having laid bare thecategorial functions in their purity, science can be judged as to itsrigor, i.e., its submission to rational legislation. The Marburgers,with this criterion in hand, enthusiastically apply it in praise andblame.

A historiographical commonplace of neo-Kantianism has it that thelabor of grounding the sciences was divided between the Marburg andSouthwest Schools, the former attending to the natural sciences, thelatter to the human sciences orGeisteswissenschaften (cf.Oesterreich 1923: 417). Recent scholarship has complicated thispicture, reminding us of Rickert’s contributions to philosophyof natural science (cf., e.g., Rickert 1902; 1899), and noting thatthe Marburg School, too, has a theory of history (esp. Edel 1994; Laks1994; Lembeck 1994). Already Cohen argues that the disciplinarydivision between systematic philosophy and the history of philosophyis artificial and harmful; he insists that “the study ofphilosophy requires the connection of the systematic and historicalinterest” (Cohen 1902: 440).

Still, the common view, if one-sided, is not wrong, for the Marburgtheory of history has a very different starting-point than does theSouthwest School. Unlike Rickert and Windelband, Cohen and Natorp donot begin their theory of history from the “fact” ofhistorical science, in the way they begin their theory of naturalscience from the “fact” of mathematical physics. When theyspeak of history, they mean, on the one hand, the historyofscience, and on the other, the historyof philosophy,properly construed, namely as the critique of science. Onlysecondarily are they interested in political, economic, or socialhistory, and only insofar as it advances their primary project.^[33]

The Marburg conception of genuine philosophy asin the firstplace a transcendental logic of natural science (cf. Cohen 1902:445) therefore restricts history to a history of “scientific idealism”.^[34] In rejecting the view that scientific progress is better understoodexclusively from a “systematic” perspective,“detache[d] … from its historical bonds”, (Cohen1902: 439) Cohen remarks that the “very value and security ofscience is rooted in its own history, connected, as it were, with thegeneral history of mind [Geist]” (Cohen 1916: 310).This sounds odd since we have heard again and again that science isrooted in itsmethod, but now are told it is rooted in itshistory. Perhaps the paradox is only seeming, for there is an intimateconnection between the Marburg School’s notion of hypothesis asthe active posit of mind, on the one hand, and its notion of scienceas essentially historical, on the other. Their conception of the logicof science as the dynamicGang of categorial hypothesesimplies that science can only be grasped developmentally, i.e.,historically.

The Marburg view of that history differs in two important respectsfrom Hegel’s, with which it might otherwise seem to have much incommon: first, it is not based upon a sequence of conceptualcontradiction and resolution; second, the history of science’sdevelopment is relativistic, that is, in principle incapable ofachieving an “absolute” resolution (Natorp 1912c: 211,ff.). Let me focus on the first of these differences. For Hegel,history is thelinear evolution ofGeist’sself-knowledge through time; the further to the right you go, the moreadvanced the stage of (self-)consciousness. These stages—the“phenomena”—ofGeist are inseparable from,indeed just are their cultural manifestations. Cohen and Natorp, too,take genuine history to be the history of rational self-consciousness,but for them this simply means reason’s transcendental,reflective consciousness of the basis of science, that is, method.This principle of lawfulness is in itself unchanging, eternal,atemporal; it is not expressed “in” phenomena, but insteadmakes possible and generates phenomena as such; and indeed (as we sawabove) generates time itself as a condition of the possibilty ofphenomena. Because its object—this rational insight intoreason’s own principle—is essentially detached from time,history for the Marburg School is not conceived with respect to time.Of course science develops in time, and may be tracked diachronicallyalong a time-line, yet its innermost core is the self-same atemporalidea, around which sciencecircles, its progressionrepresented by ever wider, but concentric orbits.^[35] Thus the history of science is itselfideal, in the sense offocusing solely upon those moments of reflective illumination whenscience becomes self-conscious—through philosophy—of itsrational foundation or transcendental nucleus. Cohen writes: “Inthe history of every science the history of scientific reason ingeneral always fulfills itself concentrically” (Cohen 1916:310). He considers the fact that each of these moments ofself-consciousness must occur in concrete circumstances and have aunique point on a real time-line to be as obvious as it is irrelevant.^[36]

The transcendental nucleus is method, and method is the meaning ofidealism; hence, idealism is born when reason becomes self-consciousof its thinking as methodical and scientific.^[37] Since this birth has a historical locus, Cohen argues,“idealism’s historical origin … conditions idealismthrough its connection with the methodological foundation of scienceno less than its material origin in methodology” (Cohen 1916: 309).^[38] Put another way, idealism connects with its methodological foundationby connecting with its historical origin (cf. Cohen 1902:450). It follows that idealism has two related historical tasks: theprimary task is to open and maintain a direct avenue to its origin.This involves the secondary task of retracing previous scientificconnections to that same primal idealism, which alone can serve as thecriterion of the “relatedness [Verwandtheit] ofdifferent phases of science” (cf. Cohen 1916: 310). The historyof idealism is therefore not of its evolution (as is the history ofscience) but of its rebirths.

The history of science is a history of often contradictory orincommensurable theories, each of which is represented inCohen’s image as a ring. Nonetheless, as scientific, the varietyof theories all express the same central, unitary activity of reason:positing hypotheses. Because of this constant unity of scientificreason, a “continuous connection of reason and the fundamentalforces [Grundkräfte] of its history is required”(Cohen 1916: 310). By “fundamental forces” Cohen justmeans Greek antiquity,^[39] specifically Plato:

Plato is the founder of the system of philosophy … because hefounded logic [in the Marburg sense], and thereby the system ofphilosophy. He is generally to be understood as the founder ofidealism. But the word, “idealism”, in the whole historyof culture, in which it has against the odds remained the guidingwatchword, has only emerged at certain illuminating turning-pointsfrom an unclear and imprecise meaning. (Cohen 1902: 446)

History’s “illuminating turning-points”, whereidealism’s meaning manifests itself clearly and distinctly, arethe moments when the generative principle of scientific knowledgeshines forth—i.e., when a critical, reflective perspective uponmethod is achieved—drawing the mind from its hyperbolic foraysback into the regular orbit of reason, when we realize that we cannotsimply be guided by the things as they appear to us. They are momentsof reason’s recollection, rebirth, and self-renewal (Cohen 1916:309).

Hence the Marburgers consider it of the utmost significance that theirheroes—especially Galileo, Leibniz, and Kant—explicitlylink their conceptions of science back to Plato. As Cohen and Natorpselect and interpret their idealistic predecessors, they seeillustrated in them the crucialimmanent role of historicalreflection in science, by which it ascends to transcendentalself-reflection upon its methodological foundation (cf. Cohen 1902:450). As Cohen puts it, “history is … a sign[Wahrzeichen] of the inner life and growth of all problems ofscientific reason as they emerge out of the root of theirmethodology” (Cohen 1916: 310); and that root is, historically,Plato: “Idealism is the Idealism of the Platonic Idea”(Cohen 1916: 305).^[40] For Cohen and Natorp, “Plato” signifies the organizingprinciple of science as a historically unfolding, living enterprise.To stop reading Plato is to subtract science from its rational core,and deprive it—not of its method, which it will always havequa science—but of self-transparency of its ownpure foundation and legitimacy.

Although history, according to Cohen, “discloses the origin ofidealism from the start”, we must rely no less upon our methodicunderstanding of idealism in order “to recognize this idealismcorrectly wherever it appears” (Cohen 1916: 305). This statementconfirms the hermeneutic inseparability of system and history: eachsupports the other. By “systematically” determiningidealism as the method of science, we enable idealism to recognizeitself in its historical manifestations; these manifestations, inturn, furnish the “fact” of science to be systematicallydetermined. This reciprocity of history and theory informs thefollowing passage, in which Cohen links Plato with the Marburgprogram.

The concept of idealism must be determined logically. Thisdetermination is the profoundest task and the highest content oflogic. Plato found this determination by establishing logic’sconnection to science, and thus grounding logic. The determinationlies in the concept of the Idea [i.e., Platonic form], themisunderstanding of which led necessarily to the indeterminacy of thenotion of idealism itself.What does “Idea”signify? (Cohen 1902: 447)

In other words, to succeed in the methodic or “logical”determination of idealism, we can do no better than ask the historicalquestion of how Plato “hits upon this determination”.

This is precisely the task Natorp sets himself inPlatosIdeenlehre [Plato’s Doctrine of Ideas]. True tothe Marburg view that idealism can only be understood by retracing itsdevelopment, Natorp simultaneously reconstructs the idealistic meaningof the dialogues and the “logical” order in which theymust have been composed.^[41] He takes a double-pronged approach by arguing, on the one hand, thatthe Platonicideai (forms or ideas) are in fact correctlyunderstood to have a “critical” sense; and, on the otherhand, by explaining why this critical intent of Plato (and byextension of all other critical idealists) was misconstrued not onlyby Aristotle and virtually the whole tradition, but even, at times, byPlato himself. That mistaken reading consists in taking the ideas tobe substances, i.e., really existent things, which however have apurely noetic, or rather, noumenal character; whose appearances (the“particulars”) may be sensible, but which in themselvesexist “separately”, open only to a quasi-mystical vision.Kant himself of course understood Plato in just this way, chastisinghim for flying beyond the limits of reason on the wings ofintellectual intuition.

Natorp by contrast argues—over the course of 500pages—that while Plato may for various reasons talk in a waythat encourages such a reading, his most mature, sober, andself-critical dialogues support acategorial interpretationof the forms as “hypotheses” in the special sensediscussed inSection 3. Thus, the problems of how the ideas could exist apart from the worldof real particulars, and whether pure reason has a special intuitivefaculty capable of bridging the gulf, evaporate, once we recognize theimmanent operation of theideai as the categorial hypotheses^[42] that are the conditions of possibility of thinking in general, and ofscience in particular. Thus Natorp interprets the supreme form, theform of the Good, as the “law of lawfulness”, (seeSection 3) i.e., the unifying source of both theoretical and practical reason,while the five “great kinds” of theSophist areseen as mutually implicative logicalGrundbegriffe or“root-categories” of all predicative thinking. Theseideai are no more separately existent, according to Natorp,than are Kant’s categories: they are not transcendent so much asthey are transcendental. It has been the incapacity of all(Aristotelian) realists or “dogmatists” to grasp thisdistinction that has led to the chronic misunderstandings of Plato andall other “criticists”.

The Marburg “theory” of history to which Natorpsubscribes, and in light of which he writesPlatosIdeenlehre, is this: Plato’s moment of insight into thetruth of transcendental idealism (à la Cohen), is followed bymillennia of dark irrelevance, punctuated by shining rings ofrecollection, epitomized by Galileo, Newton, and Kant. This picture ofMarburgPhilosophiegeschichtsphilosophie (cf. Lembeck 1994:1–2) will strike many as surreal; still, it only seems right tonote the following. Though we must understand the Marburg conceptionof history to grasp their motivation for reading and re-reading Plato,we need not accept that conception in order to appreciate eitherNatorp’s genetic logic of science or his reading of Plato. AsLembeck puts it in the introduction to hisPlaton inMarburg:

It is not a matter of proving that Plato’s philosophy is nottranscendental idealism; that is so obvious as to be taken forgranted. It is however something entirely else to show why Cohen andNatorp believe that Plato, at least in principle, laid the groundworkfor this idealism. (Lembeck 1994: 5)

Fortunately for them, we can betray theiridée fixe ofPlato as the living heart of transcendental idealism without, as theywould think, destroying or dismissing their work. Indeed, one canperhaps better appreciate the value of Natorp’s reading of Platoif one doesnot think of it as support for Marburg idealismas such, but simply as an ingenious attempt to make sense of therelation of ideal form and empirical particular, an attempt thatmerely employs the logic of categorial functions as a hypotheticalspringboard.

Bibliography

Works by Natorp

This bibliography is based substantially on that of Lembeck’s(1994), with various corrections and additions.

• 2013,Allgemeine Psychologie nach kritischer Methode, Darmstadt: Wissenschaftliche Buchgesellschaft. With new introduction and notes by S. Luft.
• 2004a,Platos Ideenlehre: EineEinführung in den Idealismus (=PI), Hamburg: Meiner. Reprint of second edition (1921g/1994).
• 2004b,Plato’s Theory of Ideas:An Introduction to Idealism, Vasilis Politis (ed.), VasilisPolitis and John Connolly (trans.), Sankt Augustin: Akademia Verlag.
• 1994,Platos Ideenlehre: EineEinführung in den Idealismus, Hamburg: Meiner. Reprint of second edition (1921g).
• 1986a, Letters from and to Natorp(1883–1921), as well as other documents, in Holzhey 1986: vol.2, pp. 141–496.
• 1986b, Manuscripts from theNachlass, in Holzhey 1986: vol. 2, pp. 5–140. Theyinclude:
  • “Zu Cohens Logik”
  • “Zu Cohens Logik (Entwurf fürDie logischenGrundlagen der exakten Wissenschaften)”
  • “Quantität und Qualität in CohensKantinterpretation”
  • “Synthetische Einheit und Ursprung (aus einer‘Einleitung zur Allgemeinen Logik’)”
  • “Zu Cohens Religionsphilosophie”
• 1985,Pädagogik und Philosophie.Drei pädagogische Abhandlungen, W. Fischer (ed.), Paderborn:Schöningh.
• 1981, “On the Objective andSubjective Grounding of Knowledge”, L. Phillips and D. Kolb(trans.),Journal of the British Society for Phenomenology,12(3): 245–266.
• 1973, “Über die Ideen E.Husserls”, in Hermann Noack (ed.),Husserl, Darmstadt:Wissenschaftliche Buchgesellschaft.
• 1965,Allgemeine Psychologie, Amsterdam:Bonset. Reprint of 1912e
• 1958,Philosophische Systematik,Hans Natorp (ed.), Hamburg: Felix Meiner Verlag. Reissued 2000.
• 1947, “Geist und Gewalt in derErziehung”, Bad Pyrmont: Friedrich Verlag.
• 1925a,Praktische Philosophie,Erlangen: Verlag der philosophischen Akademie.
• 1925b,Vorlesungen überPraktische Philosophie, Erlangen: Verlag der philosophischen Akademie.
• 1925c, “Brief an Hans Prager,Frühjahr 1924”, in “Hans Prager, Paul Natorp und dasProblem der Religionsphilosophie”,Logos, 13:186–190.
• 1923, “Fjedor DostojewskisBedeutung für die gegenwärtige Kulturkrisis”, Jena:Diederichs.
• 1922, Expanded edition of Natorp 1907c.Stuttgart: Frommann.
• 1921a,Individuum und Gemeinschaft.Mit einem Anhang, ‘Vom echten Tode’, Jena: E. Diederichs.
• 1921b, “Stunden mit RabindranathThakkur [Tagore]”, Jena: Diederichs.
• 1921c, “Beethoven und Wir”, Marburg: Elwert.
• 1921d, Review ofU. Wilamowitz-Moellendorff’sPlaton (Berlin,1921),Frankfurter Zeitung, 26 June 1921.
• 1921e, Review of C. Siegel’sPlaton undSokrates,Frankfurter Zeitung, 13 March 1921.
• 1921f, “Natorp, Paul”, inSchmidt 1921: 151–176.
• 1921g,Platos Ideenlehre. Zweite, durchsehene und um einen metakritischen Anhang vermehrte Ausgabe, Leipzig: Felix Meiner Verlag. Second edition of Natorp, 1903b. Reissued 1994, 2004a.
• 1921h, Second edition of Natorp 1910c;reissued, 1969: Wiesbaden: Sändig.
• 1920a,Sozialidealismus. NeueRichtlinien sozialer Erziehung, Berlin: Springer.
• 1920b,Genossenschaftliche Erziehungals Grundlage zum Neubau des Volkstums und des Menschentums. Thesennebst Einleitung, Berlin: Springer.
• 1920c, “Was sollen wir denntun?”Der Kunstwart, 242–249.
• 1919a,Der Idealismus Pestalozzis.Eine Neuuntersuchung der philosophischen Grundlagen seinerErziehungslehre, Leipzig: Meiner.
• 1919b,Die Einheitsschule. EineAuseinandersetzung mit Herrn Prof. Ferdinand Jakob Schmidt,Berlin: Union Deutsche Verlags-Gesellschaft.
• 1918a, “Hermann Cohensphilosophische Leistung unter dem Gesichtspunkte des Systems”,Philosophische Vorträge veröffentlicht von derKant-Gesellschaft, 21, A. Liebert (ed.), Berlin: Reuther &Reichard.
• 1918b, “Hermann Cohen als Mensch,Lehrer und Forscher”, Marburg: Elwert.
• 1918c,Deutscher Weltberuf.Geschichtsphilosophische Richtlinien, Vol. 1: “DieWeltalter des Geistes”, Vol. 2: “Die Seele desDeutschen”, Jena: Diederichs.
• 1918d, “Student undWeltanschauung”, Jena: Diederichs.
• 1918e, “Bruno Bauchs‘Immanuel Kant’ und die Fortbildung des Systems desKritischen Idealismus”,Kant-Studien, 22:426–459.
• 1915a,Der Tag der Deutschen. VierKriegsaufsätze, Hagen: O Rippel.
• 1915b,Krieg und Friede. DreiReden, Munich: Dürerbund.
• 1915c, Review of H. V. Arnim’sPlatos Jugendjahre und die Entstehungszeit des Phaidros(Leipzig, 1914),Literarisches Zentralblatt fürDeutschland, columns 486–488.
• 1915d, “GeschichtsphilosophischeGrundlegung für das Verständnis unserer Zeit”,DerKunstwart: 98–102.
• 1915e, “Zu CohensReligionsphilosophie”, in Holzhey 1986: vol. 2, pp.105–140.
• 1914a, Review of M. Wundt’sPlatons Leben und Werk (Jena 1914),LiterarischesZentralblatt für Deutschland, columns 1315–1317.
• 1914b, Review of M. Pohlenz’sAus Platos Werdezeit. Philosophische Untersuchungen (Berlin1913),Literarisches Zentralblatt für Deutschland, 4:columns 140–142.
• 1914c, “Über PlatosIdeenlehre”, Berlin: Reuther und Reichard.
• 1914d, “Hoffnungen und Gefahrenunserer Jugendbewegung”, Jena: Diederichs.
• 1913a, “Recht und Sittlichkeit. EinBeitrag zur kategorialen Begründung der praktischenPhilosophie”,Kant-Studien, 18: 1–79.
• 1913b, “Philosophie undPsychologie”,Logos, 4(2): 176–202.
• 1912a, “Willensfreiheit undVerantwortlichkeit”, in Natorp 1912b: 203–222.
• 1912b, (ed.)PhilosophischeAbhandlungen. H. Cohen zum 70. Geburtstag, Berlin.
• 1912c, “Kant und die MarburgerSchule”, inKant-Studien, 17: 193–221. Reprintedby Reuther & Reichard, Berlin, as a separate offprint fromKant-Studien.
• 1912d, “Allgemeine Logik”, inHolzhey and Flach 1980: 227–264.^[43]
• 1912e,Allgemeine Psychologie nachkritischer Methode, Tübingen: Mohr (Siebeck).
• 1911a,Philosophie. Ihr Problem undihre Probleme, Göttingen: Vandenhoeck & Ruprecht. 1918 second edition; 1921 reprint of 1918.
• 1911b,Volkskultur undPersönlichkeitskultur, Sechs Vorträge, Leipzig: Quelle und Meyer.
• 1911c, “Platon”, inGroße Denker, vol. 1: 93–152, E.V. Aster (ed.),Leipzig: Quelle und Meyer; 1921: 107–169.
• 1911d, “Zur platonischenFrage”, Reviews inDeutsche Literaturzeitung, 32:columns 1669–1677.
• 1911e, “Genesis derplatonischen Philosophie”, in Gaiser 1969:58–95.
• 1910a, Review of L. Robin’sLathéorie platonicienne de l’amour (Paris, 1908),Deutsche Literaturzeitung, columns 1748–1750.
• 1910b, “Neue französische undenglische Schriften zur platonischen Ideenlehre”,DeutscheLiteraturzeitung, columns 1285–1295; 1349–1356.
• 1910c,Die logischen Grundlagen derexakten Wissenschaften, Leipzig: Teubner. 1921.
• 1909a,Philosophie undPädagogik. Untersuchungen auf ihrem Grenzgebiet, Marburg:Elwert.
• 1909b,Pestalozzi. Sein Leben undseine Ideen, Leipzig: Teubner.1919.
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• Wolzogen, Christoph von, 1988, “‘Es gibt’.Heidegger und Natorps ‘PraktischePhilosophie.’” in Gethmann-Siefert and Pöggeler1988: 313–37.
• –––, 1984,Die autonome Relation. ZumProblem der Beziehung im Spätwerk Paul Natorps. Ein Beitrag zurGeschichte der Theorien der Relation, Würzburg: Königshausen und Neumann.
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Related Works

• Cassirer, Ernst, 1923, Second edition of Cassirer 1910.
• –––, 1912, “Hermann Cohen und dieErneuerung der Kantischen Philosophie”,Kant-Studien,17: 252–273.
• –––, 1910,Substanzbegriff undFunktionsbegriff. Untersuchungen über die Grundfragen derErkenntniskritik, Berlin: Bruno Cassirer.
• Dostal, Robert, 1985, “Beyond Being: Heidegger’sPlato”,Journal of the History of Philosophy, 23:71–98.
• Edel, Geert, 1988,Von der Vernunftkritik zur Erkenntnislogik.Die Entwicklung der theoretischen Philosophie Hermann Cohens,Freiburg/Munich: Alber.
• Friedman, Michael, 2010, “Ernst Cassirer and Thomas Kuhn:The Neo-Kantian Tradition in the History and Philosophy ofScience”, in Makkreel and Luft 2010: 177–191.
• Gadamer, Hans-Georg, 1922, “Das Wesen der Lust in denplatonischen Dialogen”, Dissertation, Department of Philosophy,University of Marburg.
• Görland, Albert, 1912, “Hermann Cohens systematischeArbeit im Dienste des kritischen Idealismus”,Kant-Studien, 17: 222–251.
• Guyer, Paul, 1992,The Cambridge Companion to Kant,Cambridge: Cambridge University Press.
• Holzhey, Helmut, 1991, “Hegel im Neukantianismus. Maskeradeund Diskurs”,Il cannocchiale. Rivista di studifilosofici, 1–2: 9–27.
• Holzhey, Helmut and Werner Flach (eds.), 1979,Erkenntnistheorie und Logik im Neukantianismus, Hildesheim: Olms.
• Kant, Immanuel, 1956,Kritik der reinen Vernunft(=KrV), R. Schmidt (ed.), Hamburg: Felix Meiner.
• Kinkel, Walter, 1912, “Das Urteil des Ursprungs: Ein Kapitelaus einem Kommentar zu H. Cohens Logik reinen Erkenntnis”,Kant-Studien, 17: 274–282.
• Lange, Friedrich Albert, 1902,Geschichte des Materialismusund Kritik seiner Bedeutung in der Gegenwart, Vol. 2:“Geschichte des Materialismus seit Kant”, Leipzig: J.Baedeker.
• Liebmann, Otto, 1865,Kant und die Epigonen. Eine kritischeAbhandlung, Stuttgart: C. Schober. Reprint: Berlin: Reuther und Reichard, 1912.
• Lindheimer, F.P., 1900,Beiträge zur Geschichte undKritik der neukantianischen Philosophie, 1st series: H. Cohen,Berne: Sturzenegger.
• Orth, E.W. and H. Holzhey (eds.), 1994,Neukantianismus:Perspektiven und Probleme, Würzburg: Königshausen &Neumann.
• Schnädelbach, Herbert, 1983a,German Philosophy:1831–1933, Cambridge: Cambridge University Press.

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